In the field of firearms, and specifically AR10, AR15 or M16 type firearms, various accessories for sighting to improve putting bullet on target, are employed. These sighting devices must be securely, rigidly and accurately attached to a firearm. To this end, firearms include an upper receiver formed of a single piece and having an upper surface designed to receive various sighting devices. The upper surface is formed as a rail for receiving and registering sighting devices. While effective, the typical rail is a Picatinny rail type that includes cross channels used for receiving and registering the sighting devices attached thereto. The formation of cross channels in the upper surface of the upper receiver thins the material of the upper receiver and can adversely affect rigidity. The slight flexibility in the upper receiver will adversely impact accuracy.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.